Java Convert Decimal to Octal

Last Updated : 17 Feb 2026

We can convert decimal to octal in java using Integer.toOctalString() method or custom logic.

Java Decimal to Octal conversion: Integer.toOctalString()

The Integer.toOctalString() method converts decimal to octal string. The signature of toOctalString() method is given below:

Let's see the simple example of converting decimal to octal in java.

//Java Program to demonstrate the use of Integer.toOctalString() method
public class DecimalToOctalExample1{
public static void main(String args[]){
//Using the predefined Integer.toOctalString() method
//to convert decimal value into octal
System.out.println(Integer.toOctalString(8));
System.out.println(Integer.toOctalString(19));
System.out.println(Integer.toOctalString(81));
}}

Output:

10
23
121

Java Decimal to Octal conversion: Custom Logic

We can convert decimal to octal in java using custom logic.

//Java Program to demonstrate the decimal to octal conversion
//using custom code
public class DecimalToOctalExample2{  
//creating method for conversion so that we can use it many times
public static String toOctal(int decimal){  
    int rem; //declaring variable to store remainder
    String octal=""; //declareing variable to store octal
    //declaring array of octal numbers
    char octalchars[]={'0','1','2','3','4','5','6','7'};
    //writing logic of decimal to octal conversion 
    while(decimal>0)
    {
       rem=decimal%8; 
       octal=octalchars[rem]+octal; 
       decimal=decimal/8;
    }
    return octal;
}  
public static void main(String args[]){    
//Calling custom method to get the octal number of given decimal value
System.out.println("Decimal to octal of 8 is: "+toOctal(8));
System.out.println("Decimal to octal of 19 is: "+toOctal(19));
System.out.println("Decimal to octal of 81 is: "+toOctal(81));
}}    

Output:

Decimal to octal of 8 is: 10
Decimal to octal of 19 is: 23
Decimal to octal of 81 is: 121

References

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